Re: Big Primaries, Small Caps

["harvey norris" <harvich-at-yahoo-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: FutureT-at-aol-dot-com 
> 
> In a message dated 9/3/00 11:37:12 AM Pacific
> Daylight Time, tesla-at-pupman-dot-com 
> writes:
> 
> > Original poster: "Gregory R. Hunter"
> <ghunter-at-accucomm-dot-net> 
> >  
> >  Dear List,
> >  
> >  I'm curious about Tesla coils with large
> primaries and small tank caps.
> >  John Freau and others have articulated numerous
> times over the years that
> >  coils so designed have lower gap losses and
> longer sparks relative to coils
> >  using big tank caps and few primary turns.  I'm
> curious as to why this is
> >  so.  It seems to me that the bigger bang size
> delivered by a larger cap
> >  would thump the secondary harder, yielding longer
> sparks.
> 
> Gregory,
> 
> I must clarify my position here:
> 
> I do not advocate the use of small primary caps
> (except
> on a very high voltage coil).  I advocate the use of
> a *large* bang
> size, with a low bps, along with a large primary
> inductance
> (usually many turns).  You are correct that a large
> bang size
> gives the best results, and this is the method I
> use.  A large
> bang size can be achieved either with a large cap,
> low voltage,
> or using a small cap with high voltage.  It's
> actually better to
> use a high voltage with small caps, since this will
> permit the
> primary surge impedance to be much higher.....
> making the
> gap losses much lower.  Most folks do not have
> access to super
> high voltage transformers however, so I normally
> speak more about
> the large cap with large primary combo (which
> demands a large
> secondary L for tuning).  The goal is to keep the
> primary surge
> impedance high which keeps the gap losses low, since
> the gap
> losses are proportional to the gap current.
> 
> The difference with what I'm advocating (vs. what is
> normally done),
> is that I recommend the use of a lot of turns of
> thinner wire in the 
> secondary which permits *both* a large primary
> capacitor and a lot
> of primary turns (high L) to be used.  This is for
> the typical voltages
> that are used.  If you have access to a super HV
> xfrmer, then you
> can use a smaller cap, with many primary turns, and
> keep the
> bang size large and the gap losses low that way.
> 
> Normally, when folks use a large capacitor, they use
> a small 
> primary L, which lets them use fewer turns of a
> thicker secondary
> wire.  This approach will reduce the secondary
> losses a little, but
> will greatly increase the gap losses, and give them
> overall shorter
> and weaker sparks.
> 
> I have stated in the past that a secondary that is
> narrow will work
> about the same as one that is wide, but I may have
> made a mistake
> there.  I'm now seeing evidence that a wider
> secondary is better up
> to a point.  But even using the wider secondary, a
> lot of turns is
> still needed for best results, at least on the small
> coils I'm working
> with.  I've obtained 42" sparks using about 550
> watts with a wide (6.5")
> secondary with 1600 turns, but a 4.2" wide secondary
> may need
> 650 watts to give the same spark length.  It is
> possible that a wide
> secondary with fewer turns (1000?) will give about
> the same spark
> length as a narrow coil with 1600 turns.  But.... if
> the wide secondary
> with 1000 turns, is re-wound with 1600 turns.... it
> will be even better.
> 
> This is all large cap, large primary Z, large bang
> work at low bps
> (around 120) for best efficiency.
> 
> One could supply the 1000 turn wide secondary coil
> with a higher
> voltage transformer, and use a smaller cap, and
> equal the efficiency
> of the wide 1600 turn secondary..    But, one could
> then install the
> 1600 turn wide secondary and most likely obtain
> *even longer sparks*.
> 
> There have been folks in the past who have advocated
> the use of a
> small primary cap with a small bang size, along with
> a high bps, but
> I am not in that camp.  My tests (at least at low
> powers) shows
> a very clear and dramatic benefit to using a large
> bang at a low
> bps. 
> 
> I am now beginning work on a new TC setup that will
> use about
> 46kV peak in the primary for even lower losses and
> greater
> efficiency.
> 
> John Freau
> ---
> 
> >  Can someone in the know provide an explanation? 
> I'm not an engineer, but I
> >  am an experienced comm/nav technician, so I can
> grasp pretty deep concepts.
> >   However, a side trip into Calculus land will
> lose me pretty quickly.
> >  
> >  Best Regards,
> >  
> >  Gregory R. Hunter
> >  
I working with high induction coils that can easily
give High BPS rates on a static gap between 180 series
resonant phased large induction coils it is seen the
the volume of the spikes(voltage amplitude by scope
inspection) showing a ring down of a high frequency
event is greatest when this occurs only twice per
cycle or 120 bps. By changing the arc gap to smaller
distance,( this may cause quenching problems in an
ordinary tesla coil) many more arcs or ring downs per
cycle can be created, but the voltage amplitude of
these are correspondingly reduced by the reduced time
period for cap charging prior to discharge in LC
oscillatory mode. Essentially by creating a more
continuous hf oscillation in time  with high bps rates
involves less energy going into each oscillation,
because of the reduced time involved for that cap
charge time. In this case instance,(not to be confused
with the typical action of a tesla primary), closing
the gap distance means that the voltage available in
the cap from the resonant rise of voltage has a lower
gate or threshold value before spilling over into a
spark discharge causing the LC oscillation. HDN


=====
Binary Resonant Systemhttp://www.insidetheweb-dot-com/mbs.cgi/mb124201

__________________________________________________
Do You Yahoo!?
Yahoo! Mail - Free email you can access from anywhere!
http://mail.yahoo-dot-com/